Batteries are EVERYWHERE, we use them EVERYDAY. Yet how many people really understand them? A campervan without batteries or electrics is... well, just a tin can. In this article, we are going deep on the campervan leisure battery. We will look at the different types of deep cycle leisure batteries (AGM, FLA, gel, and lithium ion leisure batteries), how to install leisure batteries in your van conversion, how to calculate the size of the battery, the best leisure batteries on the market, the lifespan you can expect from your batteries and how you can maximise that lifespan, and much more! By the end you will have a very thorough understanding campervan leisure batteries and be ready for your own electrical installation!
I’m Shane, a van conversion professional dedicated to helping people transform ordinary vans into homes on wheels. I've authored Roaming Home, and teach The Van Conversion Course, guiding many people through their van builds. I also write The Van Conversion Newsletter, where I share practical tips and insights. After completing two van builds and living on the road full-time since 2020, I’m excited to share my expertise with you.
So let's jump in and have a look at campervan leisure batteries!
Index
Note: Before we hop in, you might want to grab yourself a wiring diagram which you can get for free by signing up to The Van Conversion Newsletter.
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Supplies list 🛒
Note: Whilst a lithium leisure battery is preferable, it is rather expensive! As a cheaper alternative, you could get a 200Ah AGM battery instead. Though lithium is definitely superior.
 | Common connection point for positive and negative cables |
 | Leisure battery kill switch |
 | Protects the leisure battery in case of surge |
 | For monitoring the levels/health of your leisure batteries |
 | Leisure battery terminal connectors For connecting cable to your leisure battery |
What is a leisure battery?
A battery is a device that stores chemical energy, and converts it to electricity on demand. This is known as electrochemistry. To put it more simply: electricity is stored in batteries. Campervans are powered by leisure batteries - batteries which provide a steady flow of current over a prolonged period. Leisure batteries for van conversions are typically 12V and are used to power everything from the fan and fridge to heater and lights. Leisure batteries are also known as deep cycle leisure batteries; they are designed for repetitive, deeper discharges and last a long time.
Throughout this guide we will explore every aspect of campervan leisure batteries in-depth. However, if you want to cut right to the chase...
Best leisure battery for campervans
The best leisure battery for campervans are lithium iron phosphate (LiFePO4) batteries. I highly recommend the 200Ah LiFePO4 battery from Renogy.
Best Compact Size RV Battery
The LiTime LiFePO4 Lithium Battery, weighing 21lbs and is a notably small and light battery for the power it delivers. It stands out with a 100A continuous discharge/charge current and a peak of 400A. Despite lacking Bluetooth functionality, its industry-standard Group 24 size ensures easy integration into various vehicles and systems. This battery offers a 41% increase in Volumetric Energy Density (VED) and an 8X boost in Mass Energy Density (MED), making it a third lighter than equivalents. Its design allows for scalability, from 1.28kWh to 20.48kWh (16 batteries in 4P4S configuration), making it versatile for applications ranging from RVs to off-grid living. The LiTime LiFePO4 battery is a great option for those seeking to get a high quality, lightweight lithium battery without breaking the bank.
You can get a 6% discount on all LiTime products with the code VAN6.
Starter batteries vs. deep cycle leisure batteries
A starter (cranking) battery is what kicks your van into action when you turn the ignition. Starter batteries are designed to provide a big burst of energy (which the starter motor needs), the energy is supplied fast and can use as much as 20% of their total capacity per start. Once the engine starts up, the alternator recharges the starter battery so it’s ready to go for the next time you start up.
Deep cycle leisure batteries in contrast release energy in a steady flow over a longer period - as mentioned above. They are designed to withstand hundreds/thousands of charging cycles.
The anatomy of deep cycle leisure batteries
A deep cycle leisure battery is a plastic container, typically with six individual compartments inside.
Each compartment creates 2.12 Volts, therefore creating 12.7V in total for a fully-charged battery.
Each compartment contains rows of positive and negative lead plates. These are setup in a grid so that lead oxide paste can be squeezed into all the little openings. Each plate is erected in a perforated piece of plastic called a separator.
In a deep cycle leisure battery, these plates are thicker than in starter batteries; the separators also contain glass fibre sheets to squish against the lead oxide paste.
The glass fibre sheets help protect the batteries during constant re-charging (the paste can become loose and then completely come off from the lead grid).
The compartments of lead-acid batteries are filled with sulphuric acid (so be careful with these things!). Consequently, the plastic casing has a gas outlet for releasing hydrogen created during recharging (FLA batteries). Sealed lead-acid batteries do not have this outlet.
Chemical Reactions in Batteries
Leisure batteries, particularly lead-acid ones, are built on the same core components. Inside, the positive plates are made of lead oxide (PbO2), while the negative plates consist of sponge lead (Pb). The electrolyte responsible for the chemical reactions is sulphuric acid (H2SO4). When discharging, the lead oxide and sulphuric acid react to produce lead sulfate, water, and electricity.
Important Note on Battery Maintenance: If you're using a flooded lead-acid (FLA) battery, you should pay attention to its electrolyte's specific gravity. A fully charged battery should have a specific gravity of around 1.260, which helps lower the freezing point of the electrolyte to about -58°C. On the other hand, a completely discharged battery (specific gravity of 1.120) can freeze at temperatures as high as -10°C, potentially damaging the battery.
Depth of discharge and battery cycles
Deep cycle leisure batteries are designed to discharge power at a slow, steady rate over a long period of time. They are known as deep cycle batteries.
Leisure batteries can be discharged to a certain level, known as its depth of discharge (DoD), hundreds / thousands of times in their lifetime.
A single discharge is known as a cycle. Lead acid batteries can (should) typically be discharged to 50%, whereas lithium batteries can be discharged far more (to about 80%).
Sulfonation: We should be cautious never to completely drain our leisure batteries, and certainly never leave a battery in a completely discharged state. If recharging is delayed, sulfonation occurs. During sulfonation a white deposit forms on the battery’s plates. This is incurable and renders the battery useless.
Sometimes when sulfonation occurs the lead plates inside the batteries can fall over. When this happens you will see that the battery voltage falls to weird levels like 8V or lower. This is NOT normal, a deep cycle leisure battery should never be able fall below ~11V.
It is possible to bring a battery back from an event like this by charging it up (typically with a very heavy charge initially). However, the more you allow your batteries to fall flat, the worse sulfonation will get until the batteries are incapacitated.
Take good care of your batteries and your batteries will take good care of you 😇.
Regulatory Guidelines for Installing Leisure Batteries in Campervans (BS 7671 & NEC)
When installing leisure batteries in campervans, it's critical to follow established regulatory guidelines to ensure safety and compliance. These guidelines are outlined in BS 7671: IET Wiring Regulations (UK) and NEC: National Electrical Code (USA).
Below are key articles from each that apply directly to leisure battery installations in van conversions.
BS 7671 - UK Wiring Regulations
Article 721.521.1 – Flexible Wiring: Only flexible cables are permitted for DC wiring due to the movement and vibrations of vehicles. Solid core wiring (used in residential settings) is not allowed.
Article 721.55.1.1 – Isolation: An isolator switch must be installed between the leisure battery and connected loads to safely disconnect the system during maintenance or emergencies.
Article 721.411.3.1.1 – Earthing Requirements: Proper earthing is critical for DC systems in vehicles. The leisure battery’s negative terminal must be securely grounded to the vehicle chassis to prevent electrical faults.
Article 422.2.1 – Battery Ventilation: Flooded lead-acid (FLA) batteries require a ventilated enclosure to prevent the buildup of explosive gases like hydrogen. Ensure sufficient airflow with vents placed at both high and low points in the battery compartment.
Article 433.1.1 – Overcurrent Protection: Fuses or circuit breakers must be installed near the leisure battery’s terminals to protect the wiring in case of overload or short circuits.
Article 721.55.1.2 – Battery Leakage Protection: For FLA batteries, the battery compartment should be designed to prevent acid leakage from damaging other parts of the vehicle.
National Electrical Code (NEC) - United States
Article 551.30(A) – Low-Voltage DC Systems: All DC wiring must use appropriately rated cables for the current and include proper overcurrent protection. The maximum allowable DC voltage in these systems is 48V.
Article 551.20(A) – Ventilation of Battery Compartments: Flooded lead-acid batteries must be housed in ventilated compartments to avoid the accumulation of hydrogen gas, which can be explosive. Lithium batteries generally do not require ventilation.
Article 551.32(B) – Battery Interconnection: Properly sized cables must be used to interconnect multiple batteries, ensuring they can handle the combined load safely.
Article 551.40(A) – Battery Disconnect: A battery disconnect switch must be installed on the positive side of the battery circuit for safe disconnection during maintenance or emergencies.
Article 480.5 – Overcurrent Protection for Battery Circuits: Any conductor connected to the battery must have overcurrent protection (fuses or breakers) installed as close to the battery terminals as possible.
Article 110.26(D) – Terminal Protection: Battery terminals must be protected with insulating covers to prevent accidental contact, which could cause short circuits or electric shock.
General Guidelines for Leisure Battery Installations (Cross-regulation)
Battery Ventilation: Both BS 7671 and NEC require ventilation for FLA batteries to prevent the buildup of hazardous gases. Lithium batteries, which do not emit gases, typically do not require this level of ventilation.
Overcurrent Protection: Overcurrent protection (e.g., fuses or circuit breakers) must be placed as close to the battery terminals as possible in both BS 7671 (433.1.1) and NEC (480.5) to protect against electrical faults and short circuits.
Earthing: Proper earthing and bonding of the DC system is required in BS 7671 (721.411.3.1.1) and NEC (551.40). Grounding the leisure battery to the vehicle’s chassis helps prevent dangerous voltage differences during a fault.
Wiring Flexibility: Both codes emphasize the need for flexible cables (BS 7671 721.521.1, NEC 551.30(A)) in van conversions to handle the vehicle’s movement and vibrations, ensuring long-term reliability and safety.
By following these regulations, you'll ensure your campervan's leisure battery installation is safe, efficient, and compliant with industry standards, reducing risks and extending the system’s life.
Types of campervan leisure batteries (Lead-acid, AGM, Gel, Lithium, Lead-crystal)
At the highest level, there are two types of campervan leisure batteries:
1. Lead-acid batteries
2. Lithium (LiFeP04) batteries
Lead-acid batteries
Lead-acid batteries are broken down into two subcategories:
a. Flooded (open/wet) lead-acid batteries
b. Sealed (VRLA) lead-acid batteries
In the Roaming Home 2023 study, we found that of those vans with either lithium or AGM (most popular lead acid) batteries, 46% are now using lithium batteries. Compared to even five years ago this is a huge jump. The benefits of lithium batteries are substantial, even if they do come with a higher upfront cost.
Flooded lead-acid (FLA) batteries
FLA batteries emit gas (hydrogen) and thus need to be adequately ventilated. Occasionally they will need to be refilled with deionised water and must be kept securely upright! They are usually very cheap, but generally not recommended for van conversions. They have a lifespan of 4-8 years with regular maintenance.
Note: If FLA batteries are overcharged they can emit sulphuric gas which is very toxic.
Sealed lead-acid (VRLA) batteries
VRLA batteries are sealed, thus they do not need any ventilation. Similarly, they do not need any topping up with deionised water. Sealed lead-acid (or lithium) batteries are recommended for van conversions.
If we dive just a little deeper into sealed lead-acid leisure batteries, we find that we have two types:
AGM batteries (Absorbed glass mat)
Gel cell batteries
AGM batteries
AGM batteries are the cheapest type of sealed lead-acid battery. They are rugged and require no maintenance. They are the most popular type of battery for van conversions. They have a longer life than flooded lead-acid batteries and work better in colder conditions. Interestingly, AGM leisure batteries can be used as starter batteries as well as leisure batteries. You can expect to get roughly 500 charge cycles (at 50% DOD) from a typical AGM leisure battery.
Note: When recharging an AGM leisure battery, the charge voltage must not exceed 14.4V (A battery charger or solar charge controller will handle this for you).
Gel batteries
Gel cell batteries have all the benefits of AGM leisure batteries but with a longer life (if they are cared for!). However they are incredibly heavy. Gel leisure batteries operate better in warmer and colder climates than AGM leisure batteries. You can expect to get roughly 1000 charge cycles (at 50% DOD) from a gel leisure battery.
Note: When recharging an Gel leisure battery, the charge voltage must not exceed 14.2V.
AGM vs. gel cell batteries: As a rough rule of thumb, gel batteries have twice as many charge cycles as AGM leisure batteries. As we can see from the following graph, if we are careless with our batteries and discharge them 80-100% we absolutely destroy the lifespan of the battery. In contrast, if we are kind to our batteries and only discharge them 25% our batteries will last a hell of a lot longer!
Lithium ion leisure batteries (LiFeP04)
I won't beat around the bush, lithium leisure batteries are awesome. Lithium batteries provide as much energy as lead-acid batteries for a quarter the weight and smaller size! The lifespan (number of charge cycles) of a Lithium leisure battery can be up to 5 times that of a lead-acid battery and has a depth of discharge of 80%.
Lithium ion vs. Lithium iron phosphate (LiFePO4): LiFePO4 batteries are better than comparable lithium ion batteries. Lithium iron phosphate batteries are less prone to combustion, making them safer for campervan use. Plus, a longer cycle life means the LiFePO4 batteries will outlast lithium-ion by up to five times. Choose lithium iron phosphate over lithium ion.
There is no liquid in a lithium battery so they can even be mounted upside-down. They require little maintenance and charge much faster than lead acid batteries.
When paired with a smart charger, they charge up lightning quick when the engine is running - especially if you have a newer alternator. The importance of this fact cannot be understated. If you are staying stationary during winter (eg. doing a ski season in a van), and get little exposure to the sun - this is a lifesaver.
Surely there's a catch?
Yep… the price tag. Lithium batteries are up to four times the price of a lead-acid battery. However in this van converter's humble opinion: well worth the price.
As we can see from the graph below, with a DoD of 50%, we can expect to get ~1150 charge cycles from a typical lithium ion leisure battery. Though, with high quality LiFePo4 leisure batteries you could expect 3000-5000 charge cycles.
It's worth mentioning that lithium batteries function worse in very cold temperatures in comparison to lead-acid. So if you are using your van in cold locations (I’m frequently in temperatures of -20°C), make sure you keep the van warm inside!
Note: You must use a DC-to-DC battery charger when split charging lithium batteries; you cannot use a voltage sensitive relay.
Lead-crystal batteries
I'm going to give these rarer batteries an honourable mention. They are not popular in van conversions yet because they are relatively new. They have no liquid meaning there is no risk of spillage or sulfonation. They were originally designed by UPS and are around twice the price of a regular lead-acid battery.
Lead-crystal batteries charge twice as quickly as lead-acid, have more charge cycles, and appealingly can function in very extreme temperatures.
Categories (class) of campervan leisure battery
A campervan leisure battery is certified class A, B, or C - a rating given by the National Caravan Council (NCC) in the UK. ‘A’ has the longest lifespan and is designed for frequent use, ‘C’ has the shortest lifespan and is designed for infrequent use or vans that are permanently hooked up. Simply put, ‘A’ has more lead, ‘C’ has less lead.
Category A is for higher storage capacity for people who frequently use their campervans away from electrical hook-ups
Category B are aimed at those who frequently use sites with hook-up facilities, but require a greater battery capacity
Category C is for those who require a lower capacity battery, just to cover basic operation of their appliances for short periods away from a hook-up
It is worth pointing out that Category A batteries will be significantly heavier than their category C Counterpart. Weight is a good measure of quality with lead-acid batteries; the heavier, the better.
I would suggest you grab yourself a nice, heavy category A leisure battery (or a Lithium battery).
How long does a leisure battery last?
You can expect to get roughly 500 charge cycles (at 50% DOD) from a typical AGM leisure battery.
You can expect to get roughly 1000 charge cycles (at 50% DOD) from a gel leisure battery.
And finally, with a DoD of 50%, we can expect to get ~1150 charge cycles from a typical lithium ion leisure battery. Though, with high quality LiFePo4 leisure batteries you could expect 3000-5000 charge cycles.
When choosing a lead-acid leisure battery, it helps to understand a few key industry standards:
20-Hour Rate: This refers to the number of amps a battery can discharge over a 20-hour period at a constant rate, before the voltage drops below 1.75 volts per cell.
Reserve Capacity: This is the number of minutes a battery can deliver a constant 25 amps before the voltage dips below 1.75 volts per cell at 26°C.
Cold Cranking Amps (CCA): This measures how many amps a fully charged battery can maintain for 30 seconds at -18°C before voltage drops below 1.2V per cell. This is essential if you plan to use your van in cold climates.
Charging profiles of deep cycle leisure batteries
Charging profiles of deep cycle leisure batteries normally follow three stages: bulk, absorption and float. The charging limits differ between the different battery types.
Charging profile of lead acid batteries
Bulk: a fast, constant current charge up to ~80% State of Charge (SoC)
Absorption: much slower, constant voltage charge to reach 100% SoC
Float: a constant voltage charge which maintains 100% SoC by counteracting self-discharge
Charging profile of lithium batteries
The charging profile of lithium batteries differs from AGM, FLA, and gel. Lithium batteries go through two stages:
Constant current (roughly correlates with the bulk stage)
Constant voltage (roughly correlates with absorption stage)
In all leisure batteries, as the supply voltage increases, the current (amperage) falls. The voltage and current move inversely.
Note how different batteries charge best at different voltages. Lead-acid batteries (AGM, Gel, FLA) in particular require large voltages in the bulk and absorption stages of the charge profile. Lithium leisure batteries are the inverse - they require less power initially and gradually ramp up.
A solar charge controller or battery charger ensures that the voltage and amperage matches the charge stage of the battery. It is paramount that it does its job correctly.
For example, if we had four solar panels wired in series (74.4V) wired directly to our leisure batteries, we would be in for a very, very dangerous time indeed. The sulphuric acid would begin to boil and the plastic casing would start to melt. Before long you would have no campervan left.
How to maximise the life of your campervan leisure batteries
MOST IMPORTANTLY: Keep your batteries nice and charged up (>50%) to increase the number of charge cycles.
NEVER let your batteries remain fully discharged or you risk sulfonation which is an incurable disease for batteries.
Before mounting terminal clamps on the battery terminals, apply a thin layer of Vaseline to the battery’s terminals.
If you’re not currently using your campervan, make sure you use a trickle charger (keep it plugged into mains) to stop the leisure battery from completely losing charge.
If you are using flooded lead-acid batteries, make sure you regularly check that the electrolyte level covers the lead plates on the battery. If it doesn’t, make sure you top it up with deionised water.
One often overlooked aspect when charging wet lead-acid batteries is the generation of gases. As your battery charges, particularly toward the end of the cycle, the process of water dissociation releases oxygen and hydrogen. In confined spaces, these gases can form an explosive mixture if not properly ventilated. This is why ventilation is key when installing and using wet lead-acid batteries in your van.
Factors affecting the performance of leisure batteries
Temperature
The colder the temperature, the poorer the performance of the battery. The Ah rating stated on a battery is based on a temperature of 25C, with each degree lower causing a 1% drop in performance. For example, an 110Ah battery operating in 15C temperature will actually perform as a 100Ah.
Battery capacity is reduced by 50% at -30°C, but battery LIFE increases by about 60%! Battery life is reduced at higher temperatures.
Age
Most leisure batteries will not last more than ~five years and experience a decrease in performance over time.
Power consumption
If a large number of appliances (high wattage) are run from the leisure battery, it will discharge quicker and therefore need to be recharged more often. This frequent recharging will cause the battery to degrade sooner.
Specific gravity
Specific gravity is a critical indicator of a lead-acid battery's state of charge. There is a direct correlation between specific gravity and the open circuit voltage of your battery. Over time, batteries naturally lose charge due to their environment. At average temperatures, a lead-acid battery loses about 0.001 specific gravity points per day, with discharge rates increasing on hot days. This means if you leave your van idle for several weeks, you might return to a sluggish battery due to this slow, natural discharge.
Category
As mentioned before, Category B and C batteries will not last as long as Category A batteries due to there being less lead in the battery.
What size leisure battery do I need?
Calculate your total electrical load
To calculate your battery size you will first need to fill out a load sheet.
Updated 2024: We have built a new load sizing calculator which you can find here.
Or you can download a load sheet spreadsheet at TheVanConversion.com/load-sheet.
Column 1: In order to figure out the size of batteries required, we will first need to figure out all the appliances we want to have in our van. On the load sheet, list out these appliances.
Column 2: Enter the quantity you will have of each appliance.
Column 3: Enter the Voltage of the appliances; most appliances will be 12V DC, though some will be 230V/110V AC (eg. the laptop is charged through the mains plug sockets).
Column 4: Enter the Amps of each individual appliance (you can find this on the spec sheet for the appliance).
Column 5: Total Amps = quantity × Amps.
Column 6: Watts = Total Amps × Volts.
Column 7: Enter the number of hours per day you estimate you will use the appliance (Note: fridges turn on and off throughout the day, they usually run for 6-8 hours per day).
Column 8: Total Watt hours = quantity × Watts × hours used.
The output at the very bottom of the worksheet is the total Watt hours (Wh) that will be used given all our appliances. It is the sum of all the total Watt hours.
Convert Wh to Ah: We will quickly convert the Watt hours (Wh) to Amp hours (Ah) as Ah is more commonly used for sizing 12V leisure batteries.
The formula to convert Wh to Ah is: Ah = Wh ÷ V.
So given our estimated loads, Ah = 1185 Wh ÷ 12V. Which gives us ~98 Ah.
In other words, we can expect to use 98 Ah of battery power per day in our campervan.
Determine your required battery size
The calculations above showed us the total load of our devices.
However I want to be able to be off-grid for at least two days, so I'm going to multiply the Ah by two to give me 196 Ah.
One further caveat; remember we should only discharge lead-acid batteries to 50%, so we will actually need TWICE our calculated Ah. 2 × 196 Ah = 392 Ah. This gives us two full days off-grid, assuming no charging via solar or battery chargers during this time. Lithium batteries do not need to worry about this so much.
We have built a handy battery sizing calculator that you can use to figure out exactly which battery is best for you.
In keeping with some of the calculations above, I highly recommend the 200Ah lithium battery from Renogy.
In the Roaming Home 2023 study, we found that most people install 100-200Ah batteries.
How to charge a leisure battery
There are three ways of charging leisure batteries in a campervan:
Split charging system (connect to the alternator of the vehicle so you charge up while driving)
Shore power (plug into mains)
So, let's figure out how long it will take to recharge our leisure batteries with solar panels, a split charge relay, or shore power.
Battery size
Let’s say for argument's sake we have 392 Ah of leisure battery storage. We can discharge it 50% and so we will need to fill 196 Ah. Let's quickly convert this back to Wh for ease of calculation. The formula is Wh = Ah × V, which would give us 2304Wh.
Battery efficiency
Lithium batteries charge at nearly 100% efficiency, compared to the 85% efficiency of most lead acid batteries. This is due to their charging profiles. The charging efficiency of lead acid batteries gets particularly bad when they are discharged more than 50%.
Ambient temperature also has a big effect on the charging efficiency of batteries; colder temperatures lower efficiency a lot.
C-rating
A battery’s charge (and discharge) rate is controlled by its C-rating. The C-rating of a leisure battery describes the rate at which one can charge or discharge said battery safely. The C-rating (charge) of a typical lead acid battery is 0.2C, whereas the C-rating of a lithium leisure battery is typically 0.5C. We won’t go into further detail on this, but in a nutshell: we are capped at how fast we can charge (or discharge) our batteries due to their C-rating.
How long does it take to charge leisure batteries?
We have built a battery charge time calculator which you may find helpful. It will tell you exactly how long in hours it will take for a full charge given your input parameters.
How long does it take to charge leisure batteries from solar panels?
Let's say we have 4 × 100W solar panels on our van roof, giving us a total of 400W power. We know we have to fill up 2304 Wh of battery using 400W of solar power. So: 2304Wh ÷ 400 watts = 5.8 hours.
However, solar panels typically only output 70% of the rated wattage. So: 2304Wh ÷ (400W × 0.7) = 8.2 hours. If we are using lead acid batteries we would add another hour or so as lead acid batteries are only ~85% charge efficient.
How long does it take to charge leisure batteries from a split charge relay?
Split charge relay / voltage sensitive relay
As a rough average, a vehicle’s alternator typically delivers 1500W of electricity - though this can vary between 500W and 2500W depending on the make and age of the vehicle.
Using the same maths as before, 2304Wh ÷ 1500W = 1.5 hours. Hypothetically, it should only take 1.5 hours to charge the leisure battery from 50% capacity using a split charge relay (or VSR).
However, due to the C-rating of the batteries, we are capped in terms of how fast we can charge them. A lead acid battery could easily take double that time, though a lithium battery may be able to charge in that time due to its superior C-rating.
On top of this, the SCR/VSR does not deliver optimised voltage and current per the charging profile of the battery.
B2B battery charger
The wattage that a battery charger delivers is directly related to the Amp rating of the charger. B2B chargers are usually rated at 20, 40, or 60 amps. A 20A charger delivers 250W, a 60A charger delivers 750W.
A battery charger will also decrease the time it takes to charge a leisure battery by matching the voltage and current with the optimal charging profile.
Sizing your DC-to-DC charger correctly can be a little tricky so we built a smart charger calculator which should help you out.
While split charging from your van’s alternator is a great way to top up your batteries on the go, it’s important to set realistic expectations. Even if your alternator is rated for 60 amps, sustained output to your battery will likely be much lower. In fact, most setups only deliver about 50% of the rated capacity, meaning a 60-amp alternator might only charge your battery at 30 amps over time. If your battery is nearing full charge, this drops even further, with a 14.4-volt regulator only delivering around 2 amps to a fully charged battery.
How long to charge leisure battery from mains?
Next, let's figure out how long it takes to charge a leisure battery from mains! In order to charge our leisure batteries from mains we will need an AC to DC battery charger. The battery charger regulates the flow of electricity to the batteries and converts the AC into DC.
For instance if we have the Victron 30A IP22 battery charger, we can expect to fill our 196 Ah batteries in 196Ah ÷ 30A = 6.5 hours. We can add an extra hour or more to this if we are using a lead acid battery.
Balanced vs. unbalanced charging
If you have multiple leisure batteries, they are typically wired in parallel. This keeps the voltage the same (12V), but increases the amperage (or amp hours). To wire leisure batteries in parallel we simply connect all the positive terminals and all the negative terminals in a daisy chain fashion. It's possible to wire leisure batteries in series, but this produces very different results. Read more about parallel and series wiring setups here.
Use a thick cable (55 mm²) to connect all the batteries together.
It is important to configure the battery bank so all batteries are charged and discharged as equally as possible. This prevents one battery from working harder than another. This is known as balanced charging.
Above is an example of unbalanced charging, whereby the battery on the right is doing the most work. Notice how both the positive and negative feeds go to the same battery.
Instead, we should have the positive and negative feeds going to batteries on either side of the bank.
How to use a leisure battery when camping
Normally, campervan leisure batteries stay inside the vehicle, in a permanent, fixed position. Well then... How can we use a leisure battery when camping?
The answer is: portable power stations! These devices have become exceedingly popular in the last couple years and are improving constantly. Portable power stations are lithium leisure batteries you can easily take with you while camping!
We have written an extensive guide to portable power stations which you should check out if you want to learn more.
There are a few very popular brands, including Ecoflow, jackery, and GoalZero. My top pick is still Renogy - their portable power bank definitely gives you the most bang for your buck.
How to install leisure batteries in a van conversion
You can get a complete wiring diagram when you sign up to The Van Conversion Newsletter. The diagram shows you how to wire up your batteries and everything else! I send out the wiring diagram straight away.
Step 1: Install battery terminal clamps
First install clamps on the terminals of your leisure batteries. Apply a thin layer of Vaseline to the battery’s terminals before mounting the terminal clamps on the battery terminals.
Step 2: Connect the leisure batteries to positive and negative bus bars
Run a thick positive and negative cable from each bus bar to the leisure battery. The cable is connected to the bus bars and battery terminals using heavy duty lugs.
Step 3: Wire an isolator switch and terminal fuse
On the positive cable, add an isolator switch and terminal fuse (I used a 250A ANL fuse).
Don’t forget to ground your negative bus bar (or leisure battery)! This is a very important safety requirement.
How to wire 2 leisure batteries in parallel
Some people will opt for a single leisure battery, while others will opt for multiple batteries, thus increasing storage capacity. If you are using multiple batteries, make sure you wire them in parallel to keep the voltage at 12v; if you wire in series the voltage increases as a factor of the number of batteries attached. In practice, this means wire positive to positive, and negative to negative. I installed two 130aH leisure batteries wired in parallel.
Note: Don't forget to keep your battery bank balanced!
What should a 12 volt leisure battery read when fully charged?
The precise voltage of a fully charged leisure battery differs depending on the chemistry of the battery. In general, sealed lead acid batteries are fully charged >12.8V, whereas lithium batteries are fully charged >13.3V. Check out the voltage chart below.
How to test a leisure battery
There are three ways of checking the charge level of your leisure batteries:
To determine how full a leisure battery is, we look at the voltage of the battery.
Voltmeter
To see the charge of your batteries with a voltmeter, simply touch the positive node of the voltmeter to the positive terminal of the battery, and the negative to the negative.
If the voltmeter gives a reading of >12.8V you are fully charged (sealed lead acid).
Battery monitor
A more permanent way of checking the levels of our batteries is to hook up a battery monitor. It gives us lots of interesting metadata about our batteries.
To install one of these, you will need to install a 'shunt' on the negative line leading from the bus bar to the batteries. We also wire the shunt directly to the positive terminal of the leisure battery. Finally, we can connect a battery monitor to the shunt.
Charge Controller Monitor
A charge controller monitor is a device that plugs into your solar charge controller. It gives a bunch of helpful metadata on your batteries and is far easier to install than a battery monitor! If you have a Renogy MPPT, you can use the BT-2 bluetooth monitor that connects wirelessly with your smartphone.
If you are using a Victron MPPT, you will need to use the VE.Direct Bluetooth Smart dongle instead.
Conclusion
I truly hope you found this explanation of campervan leisure batteries useful! That was a lot of information! I think you now know EVERYTHING THERE IS TO KNOW about leisure batteries. You are now well equipped to build out a kickass electrical system in your own self-build campervan!
Don't forget to subscribe to The Van Conversion Newsletter for everything you need to get started with your own van conversion (I'll send you a free wiring diagram when you join).
If you're looking for some guidance with your van conversion, you might be interested in our book Roaming Home, or in our online course The Van Conversion Mastery Course. You'll learn directly from me how to convert a van into your dream home - no prior experience needed!
Until next time,
Shane ✌️
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